Watch and Clock Escapements eBook

Now this line f e is tangent to the arc a
from the point f, and consequently a locking
placed at the point f is a true tangential
locking; and if the resting or locking face of a pallet
was made to coincide with the line A f’,
such locking face would be strictly “dead”
or neutral. The intersection of the line f
e with the line A B we call the point C,
and locate at this point the center of our pallet
staff. According to the method of delineating
the lever escapement by Moritz Grossmann the tangent
line for locating the center of the pallet staff is
drawn from the point c, which would locate the
center of the pallet staff at the point h on
the line A B.

Grossmann, in delineating his locking face for the
draw, shows such face at an angle of twelve degrees
to the radial line A f’, when he should
have drawn it twelve degrees to an imaginary line shown
at f i, which is at right angles to the line
f h. To the writer’s mind this is
not just as it should be, and may lead to misunderstanding
and bad construction. We should always bear in
mind the fact that the basis of a locking face is
a neutral plane placed at right angles to the line
of thrust, and the “draw” comes from a
locking face placed at an angle to such neutral plane.
A careful study of the diagram at Fig. 88 will give
the reader correct ideas. If a tooth locks at
the point c, the tangential thrust would be
on the line c h’, and a neutral locking
face would be on the line A c.

NEUTRAL LOCKINGS.

To aid in explanation, let us remove the pallet center
to D; then the line of thrust would be c
D and a neutral locking face would coincide with
the line m m, which is at right angles to the
line c D. If we should now make a locking
face with a “draw” and at an angle to the
line c D, say, for illustration, to correspond
to the line c c’ (leaving the pallet
center at D), we would have a strong draw and
also a cruel engaging friction.

If, however, we removed the engaging tooth, which
we have just conceived to be at c, to the point
k on the arc a’ a’, Fig.
88, the pallet center D would then represent
a tangential locking, and a neutral pallet face would
coincide with the radial line A k’; and
a locking face with twelve degrees draw would coincide
nearly with the line l. Let us next analyze
what the effect would be if we changed the pallet
center to h’, Fig. 88, leaving the engaging
tooth still at k. In this instance the
line l l would then coincide with a neutral
locking face, and to obtain the proper draw we should
delineate the locking face to correspond to the line
k n, which we assume to be twelve degrees from
k l.